The present invention is directed to an elastomeric mount for use in supporting truck cabs, and the like. More particularly, the present invention is directed to a mount including cored-out sections to reduce vertical stiffness.
The prior art cab mount 18, for which the present invention improves upon is best shown in FIG. 1. The prior art mount 18 consists of a housing 20 adapted to be attached to a vehicle chassis by holes 22, 22' and a bonded component 26. The housing 20 has an axial through bore 22 with localized opposed fore-and-aft pockets 24, 24' formed therein. The bonded component 26 consists of an inner member 28 with elastomer 30 bonded thereto. A pair of such front mounts 18 are positioned on opposite sides of the cab at the front (fore) portion of the cab with their axial axes extending laterally of the chassis, thus forming a front pivot for the truck cab. Combinations of air springs and dampers are used at the back (aft) portion of the cab as is common practice. Notably, the pivotal motion at the front mounts 18 is minimal.
These mounts 18 are softest in the axial (lateral) direction, resisting lateral motion (into and out of the paper) of the cab by shearing the elastomer 30. Soft vertical stiffness is provided by upper and lower cored-out areas 32, 32' which extend laterally completely through the mount 18. Gross motions are delimited by upper and lower elastomer snubbers 34, 34'. The bonded component 26 is precompressed into the pockets 24, 24' which include radially inward projections 36a-36d at the pocket's radial ends which, together with pockets 24, 24', prevent rotation of the bonded component 26 within the housing 20. The mounts 18 provide good vertical isolation of the cab, while simultaneously carrying fore-and-aft and lateral loads and providing vertical snubbing.
Although adequate for some applications, such mounts 18 may have insufficient durability under more severe operating conditions. For example, under repeated large vertical down loads, the upper portions 38, 38' of the elastomer 30 will tend to separate and pull away from the pocket 24, 24' at these upper portions, thus losing their ability to contribute stiffness. As a result, the assembly becomes softer and any additional load results in proportionately larger deflection of the lower elastomer portions 40, 40'. This causes the lower portions to fail at a faster rate than desired.
The present invention produces the desired improved durability and service life by providing a bonded component and mount with localized notches which preferably only traverse part way across the periphery of the opposed arcuate sections in the lateral direction thereby changing the shape factor of the mount. This allows additional precompresssion to be carried on the upper elastomer portions as compared to the prior art. Allowing additional precompression, in effect, allows carrying of higher vertical loads before the upper elastomer portions pull away from the housing thereby improving overall durability and service life. In a preferred aspect, the bonded component includes an inner member having an external surface having a non-planar profile along its axial width, such as a rounded profile, for example. According to another aspect, the location of the notches are vertically offset from a fore-and-aft axis passing through the arc center of first and second arcuate sections. More preferably, the notches each include a bottom trough portion which intersects a peripheral surface of said arcuate sections at between a 30 and 50 degree angle. Upper and lower snubbers located above and below said inner member delimit vertical motions.
While this invention has been described as being useful as a cab mount for truck cabs, it could be used in other applications where an inexpensive, yet extended service life mount is desired. One particularly advantageous use would be as an engine mount. Various other aspects, features, advantages and characteristics of the present invention will become apparent after a reading of the following specification and claims.